The cat has been treated with enrofloxacin and while the veterinary surgeon asked for 15mg tablets to be dispensed the nurse misheard and counted out 50mg tablets. Even at a little over three times the recommended dose, enrofloxacin can be retinotoxic, giving this tapetal hyper-reflectivity, vessel attenuation and irreversible blindness. The key paper here is Kirk Gelatt’s from a few years ago: Enrofloxacin-associated retinal degeneration in cats.
Veterinary Ophthalmology 2001;4:99-106. Baytril is fine to use in cats as long as one sticks to the recommended dose of 5mg/kg and goes no higher!